Spaces wasn’t used as widely as OS X’s Exposé feature, but it became quite popular with a good number of users. Then Apple essentially killed the feature in Lion (OS X 10.7), replacing it with . Though Mission Control also allows you to have multiple workspaces, it’s much less flexible. For example, Spaces let you configure up to nine permanent workspaces in a 3-by–3 grid—so you always knew the virtual location of a workspace—and let you easily navigate those workspaces using keyboard shortcuts; Mission Control arranges workspaces in a single, left-to-right virtual line, and a particular workspace may disappear if you close all the windows and apps in it. In other words, it’s no longer easy to create, say, a writing space and know exactly where it sits and what it contains.

is a new app, currently in beta, that aims to bring back much of Spaces’ functionality, but it does so by using Mission Control for the underlying functionality—it just changes the way your Mission Control workspaces appear to be arranged.

The program’s preferences window (shown here) lets you configure your virtual workspace grid, from one-by-two or two-by-one up to four-by-four. You can navigate between those workspaces in one of three ways. The first is to use Go Left, Go Right, Go Up, and Go Down commands in the systemwide ReSpaceApp menu. More convenient are the configurable keyboard shortcuts. You can assign shortcuts for each direction (I use Control+Option+Command+[arrow]), as well as a shortcut that brings up a large, graphical representation of your workspace grid (shown below). With the latter, you can use the arrow keys to select the desired workspace and then press return to switch to it. (This display is also useful for quickly determining your current workspace.)

When switching workspaces, ReSpaceApp displays a smaller, Spaces-like representation of your workspace grid with an arrow pointing from the current workspace to the destination workspace. You can even choose the transition used when switching—Slide, Cube, Swap, or Flip—and the speed of that transition.

As with Mission Control, you can move a window between workspaces by dragging it against the left or right edge of your screen; unfortunately, you can’t drag a window against the top or bottom of the screen to move the window vertically between workspaces. (This limitation is due to ReSpaceApp’s reliance on Mission Control—Mission Control workspaces are arranged only horizontally.) To move a window between vertically arranged workspaces, you drag it against the left or right edge of your screen and keep holding it there—ReSpace will cycle past the last workspace on the current row to get to the first workspace on the next row, and so on. (Alternatively, you can click-hold on the window and then—while still holding—use one of the keyboard shortcuts to switch to the desired workspace. But this may involve some serious contortions, depending on your keyboard shortcuts.)